(NYPOST) — Adam Lanza’s mother taught her son how to become a killing machine who used what he learned from her about firing guns to commit one of the worst massacres in American history at a Connecticut elementary school.

Weapon-loving Nancy Lanza regularly took her awkward loner-son Adam to shooting ranges, where the painfully shy boy — who suffered from the autism-related Asperger’s syndrome — blasted away targets using his mom’s small arsenal of guns.

“She’d take them to the range a lot . . . Nancy was an enthusiast — so much so that she wanted to pass it on to her kids,” said her former landscaper and occasional drinking buddy Dan Holmes.